It is proposed that isosteric phosphonic and phosphinic acid analogues of trinucleotides be prepared for the investigation of their ability to substitute for normal codon triplets in amino acyl t-RNA binding. Based on the results of initial investigations with model analogues, further phosphinic acid analogues are to be prepared to study their ability to substitute for normal systems in protein synthesis and as initiators and terminators of protein synthesis. Basically this is a chemical approach to supplement biological methods for genetic regulation.